我們報告了帶電B介子二體衰變的分支分數與電荷宇稱破壞,包括了 B+ → K+ π0, π+ π0 衰變和它們的反粒子在Belle II實驗的測量結果。我們分析了從2019到2020,在 Υ(4S) 共振態下積分亮度共62.8反飛靶的正負電子對撞數據。 衰變分枝的測量結果為:B(B+ → K+ π0) = [11.9 +1.1 -1.0 (stat) ± 1.6(syst)] X 10^-6 以及 B(B+ → π+ π0) = [5.5 +1.0 -0.9 (stat) ± 0.7(syst)] X 10^-6。 宇稱破壞的測量結果為:ACP(B+ → K+ π0) = -0.089 ± 0.085 (stat) ± 0.025(syst) 以及 ACP(B+ → π+ π0) = -0.042 ± 0.166 (stat) ± 0.062(syst),第一項誤差為統計誤差、第二項為系統誤差。 這次的測量結果與世界的平均值一致,而且在早期顯示出良好的探測器性能。
We report on measurements of branching fractions (B) and direct CP asymmetries (ACP) for the decays, B+ → K+ π0, π+ π0 with a sample collected in 2019 and 2020 at the Υ(4S) resonance, corresponding to 62.8 fb^-1 of integrated luminosity. In this study, we use two dimensional Mbc X ΔE fitting to determine the signal yields. We obtain the following branching fractions B(B+ → K+ π0) = [11.9 +1.1 -1.0 (stat) ± 1.6(syst)] X 10-6 and B(B+ → π+ π0) = [5.5 +1.0 -0.9 (stat) ± 0.7(syst)] X 10^-6. The direct CP asymmetries are measured to be ACP(B+ → K+ π0) = -0.089 ± 0.085 (stat) ± 0.025(syst) and ACP(B+ → π+ π0) = -0.042 ± 0.166 (stat) ± 0.062(syst), where the first uncertainty is statistical uncertainty an the second is the systematic uncertainty. The results agree with world average and show a good detector performance in early stage.